1. Field of the Invention
This invention relates to a microwave powered gas laser apparatus.
2. Description of the Prior Art
In microwave powered gas laser apparatus, molecules of laser medium gas are excited to high energy states by microwave through a discharge process to provide laser oscillation. To attain a high efficiency of the laser oscillation, it is desirable to provide spatially even excitation of the laser medium gas by the microwave for the following reason. Uneven excitation tends to cause streamer discharge, extraordinarily heating of the gas in local areas, and a spatial unevenness in the laser amplification factor which result in a drop in the laser oscillation efficiency and a decrease in the maximum laser power output. It should be noted that the streamer discharge is unsuited to desired excitation.
In the excitation by the microwave through the discharge process, since the wavelength of the microwave is ten centimeters or more, it tends to be difficult to provide an even distribution of the strength (the intensity) of an electric field over a wide spatial region. The uneven distribution of the strength of the electric field results in spatially uneven discharge.
Japanese published unexamined patent application 2-130975 discloses that an insulator disposed within a waveguide for microwave restricts a glow discharge area to improve the degree of spatial evenness of the electric field of the microwave.